One purpose of this program is to examine systematically some of the conditions under which recovery of function might appear after damage to the somatosensory system. One factor which is being assessed is the duration of the recovery period following one-stage bilateral ablation of Sm-1 or Sm-2 of the rat cortex. "Overtraining" is another variable that is being studied in rats to be given cortical lesions. Work is also being conducted on tactile habit reversals in order to determine whether deficits following somatic cortex lesions are just in the sensorimotor domain, or whether they also have a "cognitive" component. In addition, the ability of young and old animals to make use of spared fragments of target tissue (somatosensory cortex) is being investigated. Projects closely related to these are examining: (a) The effects of brain damage on lifespan and susceptibility to various diseases; (b) Serial lesion effects with caudal diencephalon targets and swimming in rats (with one-stage bilateral lesions these animals show "neglect" and drown in water close to body temperature); and (c) The role of insulin injections prior to caudate nucleus lesions on recovery on a number of behavioral indices.